1. Field of the Invention
The present invention relates to a micrometer for measuring an outer diameter of an object to be measured while holding the object. Particularly, the present invention relates to a micrometer capable of easily and accurately determining whether or not any rear burr is formed on a terminal.
The present application is based on Japanese Patent Application No. Hei. 11-69063, which is incorporated herein by reference.
2. Description of the Related Art
Generally, a micrometer, which is an instrument employing a screw spindle of a very precise pitch as measuring means, is used for measuring an outer diameter of a small object. Although such a micrometer is usually used for measuring an outer diameter of an object to be measured, it is also used as a measuring instrument for determining from the measured value of the outer diameter whether or not the measured object is good as a product.
In the production of a wire harness used for transmitting a small electric power or for transferring a signal (such as data and an instruction) to an associated equipment, when a rear burr is formed on the wire harness, this wire harness is not good as a product. Therefore, the product is checked or inspected to determine whether or not any rear burr has been formed on the wire harness.
The measurement of rear burrs of a terminal has heretofore been made, alternately using two micrometers, that is, a point micrometer 100 (shown in FIG. 16) and a blade micrometer 200 (shown in FIG. 17), the point micrometer 100 including an anvil 110 having a pointed distal end, and the blade micrometer 200 including an anvil 210 and a spindle 220 each of which has a flat plate-like distal end. The different between the values, read respectively by the two micrometers, has been calculated, and the determination has been made based on it.
More specifically, first, an object 300 to be measured is inserted between the anvil 110 and a spindle 120 of the point micrometer 100, and the anvil 110 is brought into abutting engagement with the object 300 held in contact with the spindle 120 as shown in FIG. 18A, and the read value is, for example, 0.98. Then, the object 300 is inserted between the anvil 210 and the spindle 220 of the blade micrometer 200, and the anvil 210 is brought into abutting engagement with the object 300 held in contact with the spindle 220 as shown in FIG. 18B, and the read value is, for example, 1.02. The two measured values are different from each other since the position of the anvil 210 during the measurement is different from the position of the anvil of the point micrometer 100 during the measurement. Then, the difference between the two measured values is calculated, and it is determined from this difference whether or not the product is good. Namely, if the calculated difference between the two measured values is zero (0), it is determined that the product is good, and if the calculated difference between the two measured values is, for example, 0.04, it is determined that the product is defective.
Thus, in the related method, the two measured values are obtained using the two micrometers, and then the two measured values are compared with each other so as to determine whether or not any burr is present. In this method of determining the presence of burrs, the measurement is effected, alternately using the two micrometers (that is, the point micrometer and the blade micrometer), and then the difference between the two measured values is calculated, and it is determined whether or not any burr is present. Thus, the two measurements must be effected, and therefore much time is required for the measurement, and a misdetermination due to an error in the calculation often occurs, and the burrs are sometimes crushed by the measuring force (500 gf) of the flat blade. Therefore, there have been encountered problems that a mis-determination occurs, that a change of the measured value due to the shifting of the measurement position occurs, and that the determination can not be effected if a burr is formed on one side portion of the terminal.
It is an object of the present invention to provide a micrometer which is capable of effecting a measurement in a short time, and can reduce misdeterminations, and can provide the measured value in a stable manner.
To achieve the above object, according to the present invention, there is provided a micrometer which comprises a spindle having a distal end formed in a flat plate-like manner, an anvil including an anvil body formed into a rod-like shape, a pin having a diameter smaller than the anvil body and a predetermined length, the pin being formed on a distal end of the anvil body, a detection portion of a tubular shape fitted on the anvil body, the detection portion being slidably moved along the anvil body, a distal end of the detection portion is formed into a plate-like shape, and the detection portion including a pin insertion hole formed in a central portion of the distal end of the detection portion, wherein the pin is insertable into the pin insertion hole so that the pin projects from the distal end of the detection portion, and a dial gauge brought at its distal end into contact with the detection portion, the dial gauge being capable of indicating one of a plus value and a minus value in accordance with a sliding movement of the detection portion, wherein the distal end of the detection portion is abutted against the distal end of the spindle, and when a distal end of the pin of the anvil body coincides with the distal end of the detection portion, the dial gauge is set to a zero point, and wherein an object to be measured is inserted between the detection portion and the spindle. In the above micrometer, when the distal end of the detection portion is brought into abutting engagement with the object to be measured, whether the object to be measured is an appropriate one is determined from an amount of the sliding movement of the detection portion relative to the pin of the anvil body. Accordingly, the measurement can be effected in a short time, and misdeterminations can be reduced, and the stable measured values can be obtained.
Further, according to the present invention, it is preferable that the above micrometer further comprises a distal end stopper brought into contact with a distal end of the object to be measured, so as to locate the distal end of the object in a predetermined position, and a centering device which grips the object to be measured so as to center the object relative to the anvil and the spindle when the distal end of the object to be measured is abutted against a distal end of the distal end stopper. In this micrometer, the object to be measured is abutted against the distal end stopper so that the object is located in a predetermined position, and is gripped to be located in a centered position between the anvil and the spindle, and then the distal end of the detection portion is brought into abutting engagement with the object to be measured, so that whether the object to be measured is an appropriate one is detected from an amount of the sliding movement of the detection portion relative to the pin of the anvil body. Accordingly, the object to be measured can be easily located in the predetermined position, that is, in the axes of the anvil and the spindle, and therefore the measurement can be effected in a short time, and misdeterminations can be reduced, and the stable measured values can be obtained.
Further, according to the present invention, it is preferable that the distal end stopper is constituted by a micrometer. With this construction, when the distal end of the object to be measured reaches the measurement position, it is prevented from further moving beyond the measurement position, and therefore the distal end of the object to be measured can be easily and accurately located in the measurement position.
Further, according to the present invention, it is preferable that the centering device straddles the distal end of the anvil at the distal end of the spindle, and grips the object from upper and lower sides of the object at distal end measuring portions of the spindle and the anvil intersecting a direction of insertion of the object, thereby centering the object. With this construction, the distal end of the object to be measured can be easily located in the axes of the anvil and the spindle.
Still further, according to the present invention, it is preferable that the centering device comprises a pair of upper and lower claws which hold the object to be measured therebetween from upper and lower sides of the object, and the pair of claws can be moved toward and away from each other by moving a lever upwardly and downwardly. With this construction, the distal end of the object to be measured can be located in the axes of the anvil and the spindle with one touch.
Furthermore, according to the present invention, in the micrometer, whether any burr is present is determined by detecting the amount of the sliding movement of the distal end of the detection portion relative to the distal end of the pin of the anvil body. Accordingly, whether or not any burr is present can be positively determined.